Chevy Volt On Track and Meeting Goals As Vigorous Testing Proceeds, Says GM
By John O'Dell November 17, 2009Car is Heavier Than Chief Engineer Would Like, but There's Time to Slim Down
Video of Volt battery pack crush test shows just one of the scores of indignities the packs have been subjected to in an effort to find any flaws before they go into production cars.
By John O'Dell, Senior Editor
With a year to go before production begins on the 2011 Chevrolet Volt, General Motors has 80 prototypes running around the country to test the critical battery and power electronics systems and program managers say they're happy with what they re seeing - except, perhaps, around the car's waistline.
There have been problems - mostly small ones that have been resolved - Volt's new chief engineer, Andrew Farah, said in a media briefing this afternoon.
One ongoing concern is weight - the battery pack still weighs in at more than 400 pounds, and the car is heavier than Farah would like. Although not critical to the launch, it's an important issue as every pound of weight eats into fuel economy and battery range.
Farah (left, with pre-production Volt model) wouldn't say what the actual or target weights are for the car, GM's first extended-range, plug-in hybrid.
He did say that efforts to slim down the Volt are ongoing.
Farah also continued to support the company's controversial claim that the Volt could qualify for a 230 MPG city-cycle rating under an early proposal for one of the new federal fuel economy tests being developed for cars that use rechargeable batteries and electric motors some or all of the time.
We continue to shake our heads, suspecting that the claim is likely to come back and bite GM, hard, when real drivers get out there and find that a lot of fancy slow-motion driving tricks will be needed to come close unless then never drive hard or far enough to deplete the batteries and religiously charge them up every night
Among the lesser, and resolvable problems has been that the car's quiet operation in the all-electric mode revealed some noise and vibration issues that would not have been apparent in a noisier car with a conventional powertrain drowning out some of the exterior road and wind noise and mechanical humming and thrumming that affects every vehicle.
Volt prototype undergoing a "full body" endurance test involving shaking, bumping, twisting, and whatever else GM engineers can throw at it.
Engineers had to replace some off-the-shelf polymer bushings with hydraulic dampers and beef up sound dampening to quit the noise from the Volt's on-board engine-generator, for instance.
The generator, a 4-cylinder GM engine used to generate power when the Volt's battery is depleted, doesn't kick on very often in normal use so the noise, although modest, was jarring when it did, Farah said.
The Volt is designed to run for up to 40 miles on batteries alone - the distance will depend heavily on speed and driving styles - and carries the gas engine to continue generating power on trips that exceed the battery's capabilities.
GM's battery specialists also have "tweaked" the battery chemistry a bit to help improve battery life, said Bill Wallace, head engineer for GM's Voltech Battery Systems.
In all, the lithium manganese chemistry has been adjusted four times, he said, as engineers aim to ensure that even batteries operating in the coldest and hottest conditions will beyond their rated 10 years.
Video shows Volt battery pack being sprayed with a saline solution in a corrosion test.
Heat is a lithium-ion battery's worst enemy, and while GM has been able to control internal conditions in the flat lithium polymer cells and the assembled battery pack, it can't control external conditions,Wallace said.
"You don't want to leave it parked at Sky Harbor Airport [in Phoenix, Ariz.] all summer," he quipped, adding that "even if you live in Phoenix, as long as you charge [the battery pack] at night and run during the day, your battery will remain happy."
GM has assembled and is testing more than 300 battery packs made from the lithium-ion cells produced by the Volt's south Korean supplier, LG Chem, Wallace said.
A battery plant built with some of the $241 million in federal advanced technology vehicles manufacturing program loans GM has received is slated to open in January with the first Volt batteries rolling off the line in February, he said.
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